A degassing event at Brimstone Pit at NW Rota-1 volcano released an extraordinary number of bubbles.

A degassing event at Brimstone Pit at NW Rota-1 volcano releases an extraordinary number of bubbles, probably carbon dioxide. The yellow parts of the plume (seen here in the background) contain tiny droplets of molten sulfur. Click image for larger view and image credit.


SRoF'06 Science Party Explorers.

Submarine Ring of Fire 2006 Science Party Explorers:
Front row (from left): Susan Merle, Andra Bobbitt, Leigh Evans;
Row 2: Lori Savage, Ko-ichi Nakamura, Julie Huber, Sharon Walker;
Row 3 (kneeling): Ron Greene, John Dower;
Row 4: Verena Tunnicliffe, Joe Resing, Bob Embley, Dave Butterfield, Sheryl Bolton, Cornel de Ronde, Bill Chadwick;
Row 5: Boku Takano, Ben Larson, Rick Davis, Nick Deardorff, and Nathan Buck.
Click image for larger view and image credit.


Submarine Ring of Fire 2006: Mariana Arc
Mission Summary

April 18 - May 13, 2006

Bob Embley
Chief Scientist — Submarine Ring of Fire Expedition 2006
Geophysicist
NOAA Vents Program, Pacific Marine Environmental Laboratory

Read the SRoF'06 Final Cruise Report (8.5 Mb, PDF)

camera icon SRoF'06 Exploration Highlight Video (Quicktime, 272.1 Mb)

After all the months of preparation, the extremely exciting Submarine Ring of Fire 2006 (SRoF'06) expedition on the research vessel (R/V) Melville with the Jason II remotely operated vehicle (ROV), the hectic follow-up period of responding to the media requests for stories on the eruption — we can now reflect on this rich experience. When we departed Guam on April 18, we had high expectations, but I don't think any one of us suspected the full magnitude of the discoveries we were about to make. We really pushed the envelope of exploration on one of Earth's most extreme environments: the shallow submarine volcanoes of the Mariana arc.

The ongoing eruption of NW Rota-1 volcano (after at least two years!) was obviously the highlight of the cruise. The video taken during our dives here became well known throughout the world in the weeks following our expedition, both on the internet and on various television broadcasts. When we drove into the crater of Brimstone Pit on April 23 Greenwich Mean Time (GMT) during Dive 187, the activity appeared to have almost ceased. But over the next few days the activity built until it was a full-scale eruption — more active than on either of our previous two expeditions. The volcano was belching red rock extrusions of lava and sudden bursts of gas and ash particles that, at times, enveloped the Jason II ROV. The small hydrophone we deployed nearby recorded, for the first time, the sounds of a sea-floor eruption concurrent with visual observations. However, what was perhaps the most amazing part of the experience was the fact that we could actually observe it! It is unlikely that a similar eruption on a volcano above sea level could have been observed and sampled as thoroughly as we were able to do.

The next big surprise came at Daikoku, a volcano that was not thought to be particularly active during the previous (and relatively brief) visits in 2004 and 2005. The discovery of the "Cauldron" sulfur pond was extraordinary. It provided us with a unique window into what we now believe is an extensive subsurface infiltration of molten sulfur within many of the active arc volcanoes.

The southern Mariana Arc submarine volcanoes visited on the SRoF'06 expedition.

The southern Mariana arc submarine volcanoes visited on the SRoF'06 expedition. The Jason II remotely operated vehicle (ROV) dives at Seamount X, Forecast, NW Rota-1, Esmeralda Bank, Ruby, and East Diamante are indicated. Click image for larger view and image credit.


The northern Mariana Arc submarine volcanoes visited on the SRoF'06 expedition.

The northern Mariana arc submarine volcanoes visited on the SRoF'06 expedition. The Jason II ROV dives at Daikoku, NW Eifuku, and Nikko are indicated. Click image for larger view and image credit.


Nikko is a special place. We had first seen active molten sulfur flows on the sea floor here in November 2005, during the dives with the JAMSTEC (Japan Agency for Marine-Earth Science and Technology) ROV Hyper-Dolphin. Further discoveries awaited us this year. The chemosynthetic life in Nikko's crater and on its upper flanks is probably at the highest density observed to date on any sea-floor volcano. We also discovered a new molten sulfur site outside the crater (named Naraku). There was an extensive pool of molten sulfur at this site, discovered when Jason II broke through a thin crust and instantly added 80 lbs to its weight! A striking visualization at this site was the discovery of inactive ornamented sulfur chimneys.

The pond of molten sulfur discovered at Daikoku volcano is about 15 feet long and 10 feet wide.

The pond of molten sulfur discovered at Daikoku volcano is about 15 ft long and 10 ft wide. The temperature of the molten sulfur was measured at 187°C (or 369°F). Click image for larger view and image credit.


A striking visualization at this site was the discovery of inactive ornamented sulfur chimneys.

A striking visualization at Nikko was the discovery of inactive ornamented sulfur chimneys. This one is sitting on end in the middle of a huge field of tubeworms. Click image for larger view and image credit.


We also explored hydrothermal vents at the summits of four new sites (Forecast, Seamount X, Esmeralda, and Ruby) and revisited two other sites discovered in 2004 (NW Eifuku and East Diamante). The ecosystems at these and the other volcanoes along the arc continue to be of great interest to the biologists. The discoveries made at the volcanoes visited for the first time add new information as well as raise new questions. Forecast and Seamount X are geographically close (10 km apart), but their biological communities differ. The diversity of biology at Forecast is similar to that at other backarc spreading center sites (including Alice Springs several hundred kilometers north). The biology at Seamount X is similar to other seamounts on the frontal volcanic arc, which have a relatively lower diversity of species.

Some Thoughts for Future Explorations

We want to return to the Mariana arc because our brief visits to the exciting and diverse array of active sites have raised more questions than they have answered. The experience at NW Rota-1 volcano taught us that we could learn much more at such an active site if we had some other tools available to us. For example, there is still the major question of how the deep plume, which we have now observed around the volcano in both 2004 and 2006, is linked to the eruptions at the summit. In order to investigate such a linkage, we will have to collect data in both synoptic and time-series modes. For the former, we need to observe both the summit and flank activity at the same time. For example, if we had an autonomous undersea vehicle on board, we might have been able to conduct surveys with it on the flank concurrently with observations of the summit with Jason II. Time-series measurements of seismic activity and water column properties over a period of months to years could provide linkages between the eruption processes, as recorded in both the solid earth and the overlying water column. Such synoptic and time-series measurements are new modes of exploration specific to active sites, such as NW Rota-1, that we hope to implement on a future expedition.

 

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